1. Field of the Invention
The present invention relates to an ink jet print head including a plurality of ink ejecting orifices which are formed at a desired shape and a uniform size by only once using a plating technique of a metal, having an excellent productivity and a low manufacturing cost. The invention also relates to a method of producing the ink jet print head.
2. Description of the Related Art
Generally, in operation, an ink jet printer makes a light noise and shows an excellent resolution. In addition, the ink jet printer can provide a colorful printed matter at a low cost. Accordingly, the ink jet printer is relatively well developed and broadly sold as compared with a dot matrix printer or a laser printer in the field of a personal computer market. Also, a manufacturing technique of a print head that is an important component of the ink jet printer makes rapid progress in the last ten years due to the development of a semiconductor manufacturing technique. As a result, a print head having about 300 nozzles for ejecting ink and capable of providing 600 dpi resolution can be produced as it is mounted to a disposable ink cartridge.
This assignee of the present invention and the others disclose the art of a thermal ink jet print head construction in the bulletin issued by the IEEE International Electron Device Meeting, p601, 1995, the disclosure of which is herein incorporated by reference. FIGS. 15 and 16 show this thermal ink jet print head. That is, FIG. 15 is a sectional view of the thermal ink jet print head, and FIG. 16 is a perspective view of the ink jet print head shown in FIG. 15, showing the positions and the shapes of an ink channel, an ink cavity and an ink ejecting orifice. Hereinbelow, a structure and an operating principle of the ink jet print head according to the prior art will be briefly explained with reference to the above document and FIGS. 15 and 16.
Typically, ink approaches toward a front surface of a substrate 101 of an ink jet print head 100 through a first ink channel 102 from a rear surface of substrate 101 of ink jet print head 100. The ink supplied through first ink channel 102 flows along a second ink channel 103 defined by a barrier layer 108 and a nozzle plate 109, and then enters into an ink cavity 104. The ink temporarily contained in ink cavity 104 is instantaneously heated by heat generated from a resistance element 106 disposed below a protective layer 105. At this time, a part of the ink contained in ink cavity 104 is forcibly ejected out of inkjet print head 100 through an ink ejecting orifice 107, which is formed at a predetermined position above ink cavity 104, by air bubbles generated in the ink due to the heat.
In ink jet print head 100 as described above, barrier layer 108 and nozzle plate 109 are important factors capable of determining the whole flowing characteristic of the ink fluid. That is, barrier layer 108 and nozzle plate 109 have an effect upon a flow of the ink, an ejecting shape of the ink, a satellite characteristic and an ink ejecting frequency characteristic, etc. Therefore, a variety of researches in relation to the quality, the shape and the manufacturing methods of barrier layer 108 and nozzle plate 109 have been performed.
The present time, the manufacturing methods of the ink jet print head in relation to the barrier layer and the nozzle plate can be classified into a method for manufacturing a hybrid ink jet print head and a method for manufacturing a monolithic ink jet print head. According to the method for manufacturing the hybrid ink jet print head, a substrate and a nozzle plate are separately produced and thereafter they are combined together using a certain adhesive agent. In other words, the nozzle plate is separately produced and thereafter it is aligned on the substrate on which a barrier layer made of polymer is laid. Under this state, the nozzle plate is attached to the substrate using the adhesive agent. Alternatively, the nozzle plate and the barrier layer are produced as one body, and thereafter they are aligned on the substrate. Under this state, they are attached to the substrate by using the adhesive agent. According to the method for manufacturing the monolithic ink jet print head, the barrier layer and the nozzle plate directly grow up on the substrate.
The methods for manufacturing the hybrid ink jet print head are disclosed in U.S. Pat. No. 4,694,308, issued to C. S. Chan et al. on Sep. 15, 1987, and disclosed in the bulletin issued by the IEEE Solid-State Sensor and Actuator Workshop, pp200xcx9c204, 1996, of Christopher C. Betty entitled xe2x80x9cA chronology of thermal ink-jet structuresxe2x80x9d, the disclosures of which are herein incorporated by reference.
The methods for manufacturing the monolithic ink jet print head are disclosed in U.S. Pat. No. 4,438,191, issued to Frank L. Cloutier et al. on Mar. 20, 1984, and disclosed in the bulletin issued by the IEEE International Electron Device Meeting, p601, 1995, of this assignee of the present invention et al. entitled xe2x80x9cA monolithic thermal ink-jet print head utilizing electrochemical etching and two-step electroplating techniquesxe2x80x9d, the disclosures of which are herein incorporated by reference.
With reference to the above documents, a primary advantage of the method for manufacturing the monolithic ink jet print head over the method for manufacturing the hybrid ink jet print head, is that it is unnecessary to have a mandrel made of stainless steel required to plate the nozzle plate. As a result, there are no subordinate steps required to separate the mandrel from the nozzle plate. Further, it is unnecessary to provide any adhesive agent consumed to attach the nozzle plate to the substrate. Thereby, there are no working steps and equipments for combining the nozzle plate and the substrate with each other using the adhesive agent. In addition, it is possible to elaborately align the substrate, the barrier layer and the nozzle plate with one another. Therefore, it is possible to reduce the manufacturing steps of the ink jet print head. Thereby, the manufacturing cost thereof is reduced and the productivity is enhanced. In addition, the method for manufacturing the monolithic ink jet print head is adapted to manufacture an ink jet print head for a high resolution, which necessitates an elaborate alignment.
FIGS. 17A to 17C illustrate schematically a sequence of manufacturing steps of a monolithic ink jet print head according to a prior art Hereinbelow, the sequence of manufacturing steps of the monolithic ink jet print head will be briefly explained with reference to FIGS. 17A to 17C.
A first seed metal layer 301 for plating a metal barrier layer is deposited on a substrate 101 in which a resistance element 106 and a protective layer 105 are formed. In the formation of first seed metal layer 301, an upper surface of protective layer 105 is plated with titanium at a thickness of about 200 xc3x85 to provide good adhesion. And thereafter, gold is deposited thereon at a thickness of about 2,000 xc3x85. Following formation of first seed metal layer 301, first photoresist molds 302,303 are formed on first seed metal layer 301 by using photolithography technique. In a subsequent process step, first photoresist molds 302,303 are etched with HF to provide an ink channel and an ink cavity. At this time, the height of first photoresist molds 302,303 is about 30xcx9c40 xcexcm. This height is the same as that of the ink channel and the ink cavity.
Following formation of first photoresist molds 302,303 on first seed metal layer 301, a metal barrier layer 108 is deposited on first seed metal layer 301 by plating of Ni up to the height of first photoresist molds 302,303. Thereafter, a second seed metal layer 304 for a secondary plating of a metal is deposited on metal barrier layer 108 and first photoresist molds 302,303 in accordance with the same forming method as that of first seed metal layer 301.
Following formation of metal nozzle plate 109, second photoresist mold 305, second wetting layer 304, first photoresist molds 302, 303 and first wetting layer 301, which are located in barrier layer 108 and nozzle plate 109, are etched with HF in sequence. Consequently, an ink ejecting orifice 107, an ink cavity 104 and a second ink channel 103 are formed and thereby a passage allowing the ink to flow is created. Thereafter, in order to prevent barrier layer 108 and nozzle plate 109 from being corroded by the ink following along the passage, anti-corrosion plating is performed. As a result, barrier layer 108 and nozzle plate 109 are completely produced. Finally, a first ink channel 102 is formed in substrate 101 using electrolyte polishing, and thereby a print head 100 having a complete structure is manufactured.
Following formation of metal nozzle plate 109, second photoresist mold 305, second seed metal layer 304, first photoresist molds 302,303 and first seed metal layer 301, which are located in barrier layer 108 and nozzle plate 109, are etched with HF in sequence. Consequently, an ink ejecting orifice 107, an ink cavity 104 and a second ink channel 105 are formed and thereby a passage allowing the ink to flow is created. Thereafter, in order to prevent barrier layer 108 and nozzle plate 109 from being corroded by the ink flowing along the passage, anti-corrosion plating is performed. As a result, barrier layer 108 and nozzle plate 109 are completely produced. Finally, a first ink channel 102 is formed in substrate 101 using the electrolytic polishing, and thereby a print head 100 having a complete structure is manufactured.
However, the process for forming the barrier layer and the nozzle plate as described above is complicated. Accordingly, the confidence of work and the productivity deteriorate. In addition, there are several disadvantages in the process. That is, due to the heat generated during performing the vacuum depositing process for forming second seed metal layer 304 or performing the process for forming second photoresist mold 305, the shapes of first photoresist molds 302,303 can be changed and thereby second seed metal layer 304 can be cut. Further, when metal barrier layer 108 consisted of Ni is deposited up to the height of first photoresist molds 302,303, it is difficult to align the height of metal barrier layer 108 with that first photoresist molds 302,303 on a substrate having a wide area.
The present invention is contrived to solve the foregoing problems. It is a first object of the present invention to provide a method of producing an ink jet print head including a plurality of ink ejecting orifices which are formed at a desired shape and a uniform size by only once using a plating technique of a metal, having an excellent productivity and a low manufacturing cost.
In order to achieve the above first object, the present invention provides a method of producing an ink jet print head, comprising the steps of:
(a) preparing a substrate including a resistance element for heating ink therein and including a seed metal layer deposited an upper surface thereof;
(b) forming a photoresist mold on the seed metal layer;
(c) forming a metal barrier layer on one part of the seed metal layer and the photoresist mold;
(d) etching the one part of the seed metal layer and the photoresist mold in order to form an ink flowing passage within the metal barrier layer; and
(e) etching the other part of the substrate in order to form a main ink channel which is fluid-communicated with the ink flowing passage.
Preferably, the method further comprises the step of (f) anti-corrosion plating an inner surface of the ink flowing passage in order to prevent the metal barrier layer from being corroded by the ink flowing along the ink flowing passage.
The ink flowing passage includes an auxiliary ink channel, an ink cavity and an ink ejecting orifice, which are fluid-communicated with one another.
Preferably, the photoresist mold includes a first photoresist mold corresponding to the auxiliary ink channel and a second photoresist mold corresponding to the ink cavity.
Preferably, the photoresist mold includes a first photoresist mold corresponding to the auxiliary ink channel, a second photoresist mold corresponding to the ink cavity, and a third photoresist mold corresponding to the ink ejecting orifice.
Preferably, the step of (b) forming the photoresist mold, comprising the steps of:
(g) coating a photoresist on the substrate prepared in the step of (a) preparing the substrate;
(h) heat-treating the substrate on which the photoresist is coated;
(i) firstly irradiating the heat-treated substrate with the ultraviolet rays by using a first photo mask on which patterns corresponding to an ink channel and an ink cavity are formed;
(j) secondly irradiating the firstly irradiated substrate with the ultraviolet rays by using a second photo mask on which a pattern corresponding to an ink ejecting orifice is formed; and
(k) forming a photoresist mold having a three-dimensional structure by developing the secondly irradiated substrate at a stroke.
Alternatively, the step of (b) forming the photoresist mold, comprising the steps of:
(g) coating a photoresist on the substrate prepared in the step of (a) preparing the substrate;
(h) heat-treating the substrate on which the photoresist is coated;
(i) firstly irradiating the heat-treated substrate with the ultraviolet rays by using a first photo mask on which a pattern corresponding to an ink ejecting orifice is formed;
(j) secondly irradiating the firstly irradiated substrate with the ultraviolet rays by using a second photo mask on which patterns corresponding to an ink channel and an ink cavity are formed; and
(k) forming a photoresist mold having a three-dimensional structure by developing the secondly irradiated substrate at a stroke.
Further, it is a second object of the present invention to provide an ink jet print head including a plurality of ink ejecting orifices which are distributed on a wide wafer and has a desired shape, a uniform size and a high sectional height, which are adapted to an optimum ejection of the ink.
In order to achieve the above second object, the present invention provides an ink jet print head comprising:
a substrate having a resistance element for heating ink therein, a seed metal layer deposited on an upper surface thereof, and a main ink supplying passage allowing the ink supplied from an ink source to flow therethrough; and
a metal barrier layer having an ink ejecting orifice for ejecting the ink contained in an ink cavity out of the ink jet print head, the metal barrier layer upwardly extending from the seed metal layer, the metal barrier layer refining an auxiliary ink channel and the ink cavity with the aid of an upper surface of the substrate in order to flow the ink being introduced through the main ink supplying passage.
The ink ejecting orifice has a circular shape, a triangular shape or a quadrangular shape.
As described above, according to the present invention, in the manufacturing process of the ink jet print head, by only once using the patterning process of the photoresist mold or the patterning process of the photoresist mold having the three-dimensional structure and by only once using the plating technique of the metal, the ink channel, the ink cavity and the ink ejecting orifice capable of allowing the ink to flow can be formed. Further, when the patterning process of the photoresist mold having the three-dimensional structure is used in order to manufacture the ink jet print head, the metal plating is converged around the photoresist mold protruding as the shape of the ink ejecting orifice. As a result, the plurality of ink ejecting orifices formed on the wide wafer have the uniform size, the desired shape and the high sectional height which are adapted to the optimum ejection of the ink.